PHP: remove duplicate elements from a multi-dimensional array

PHP’s array_unique() is great for removing duplicates from a flat array, but it chokes on multi-dimensional arrays. If you have nested data and need to remove duplicates, here’s a clean one-liner that does the job.

The trick: serialize, unique, unserialize

The idea is straightforward: flatten the array temporarily by serialising each element, let array_unique() do its thing on the flat list, then unserialise everything back to its original structure.

$uniqueArray = array_map("unserialize", array_unique(array_map("serialize", $array)));

Working from the inside out:

• array_map("serialize", $array) — turns each nested element into a string representation
• array_unique() — removes duplicate strings (which means duplicate nested structures)
• array_map("unserialize", ...) — restores each string back to its original PHP value

The result is a multi-dimensional array with all duplicate entries removed, regardless of how deep the nesting goes. You keep the original structure and no external libraries needed.

Hope it helps!